Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$206.48	7.687%	$222.3521	$222.35	$222.35	$222.40
Purchase #2	$179.37	4.366%	$187.2013	$187.20	$187.20	$187.20
Purchase #3	$76.39	12.533%	$85.964	$85.96	$85.95	$86.00
Purchase #4	$193.58	11.793%	$216.4089	$216.41	$216.40	$216.40
Purchase #5	$166.57	3.320%	$172.1001	$172.10	$172.10	$172.10
Purchase #6	$64.28	7.643%	$69.1929	$69.19	$69.20	$69.20
Purchase #7	$123.73	3.278%	$127.7859	$127.79	$127.80	$127.80
7 purchase totals =	$1,010.40		$1,081.0052	$1,081.00	$1,081.00	$1,081.10